class_docstr: Initialise a XMLBIFWriter object.
  
  Parameters
  ----------
  model: BayesianNetwork Instance
      Model to write
  
  encoding: str (optional)
      Encoding for text data
  
  prettyprint: Bool(optional)
      Indentation in output XML if true
  
  Examples
  --------
  >>> from pgmpy.readwrite import XMLBIFWriter
  >>> from pgmpy.utils import get_example_model
  >>> model = get_example_model('asia')
  >>> writer = XMLBIFWriter(model)
  >>> writer.write_xmlbif('asia.xml')
  
  Reference
  ---------
  [1] https://www.cs.cmu.edu/afs/cs/user/fgcozman/www/Research/InterchangeFormat/
docstr: Inplace prettyprint formatter.
docstr_tok: ["Inplace","prettyprint","formatter","."]
code: def indent(self, elem, level=0):
      """
      Inplace prettyprint formatter.
      """
      i = "\n" + level * "  "
      if len(elem):
          if not elem.text or not elem.text.strip():
              elem.text = i + "  "
          if not elem.tail or not elem.tail.strip():
              elem.tail = i
          for elem in elem:
              self.indent(elem, level + 1)
          if not elem.tail or not elem.tail.strip():
              elem.tail = i
      else:
          if level and (not elem.tail or not elem.tail.strip()):
              elem.tail = i
  
imports: import xml.etree.ElementTree
  from io import BytesIO
  from itertools import chain
  import numpy
  import pyparsing
  from pgmpy.factors.discrete import State, TabularCPD
  from pgmpy.models import BayesianNetwork
  from pgmpy.utils import compat_fns
label_desc: Use image node_id 3 for calling the XMLBIFWriter obj's underlying member method code with example usage: obj.indent(elem, level) without return types